G UN- C OTTON.— Applications.
131
explosion would bo greater—it was found that theproportion of the nitric oxide diminished, whilethe nitrogen increased. As this appeared to showthat the deoxidation of the nitrogen was broughtabout by greater pressure, Lieutenant von Kap.olyiperformed the explosion in a vessel, which was soarranged as to give way just when the full power ofthe gases produced was felt, this vessel being placedin an iron globe exhausted of air. The followingtable shows the composition of the gases obtainedin this way :—-
By Volume.
By Weight.
Carbonic oxide,.
. 28-95 ....
29-97
Carbonic acid,.
. 20*82 _
33*86
Marsh gas,.
.... 7-24 ....
4-28
Hydrogen,.
Nitrogen,.
. 3-16 ....
0-24
. 12-67 ....
13-16
Aqueous vapour,....
16*87
98-18 ....
98*38
The difference between these numbers and 100 YonKarolyi reckoned as separated carbon. 100 grainsof the gun-cotton yielded about 325 cubic inches ofgaseous matter at ordinary temperature, supposingthe various products to remain in the conditionof gas. It will be observed that the products ofexplosion contain no solid substances.
By varying the conditions of pressure, confine-ment, &c., under which the combustion took place,Abel succeeded in obtaining a still greater diversityin his results. In these experiments the resultinggases were more complex in character than thoseobtained by Yon Karolyi, and generally containednitrous acid, nitric oxide, and cyanogen. As oneresult of his work, Abel produced fuses and slowmatches of gun-cotton, in which the time occupiedin burning could be accurately regulated.
Having thus stated the principal properties 0 fgun-cotton, we proceed to give some informationas to its applications.
From the time of its discovery by Sciionbein,attempts have been made to use gun-cotton inartillery, but with varying success. When a loose massof gun-cotton is ignited in the air it burns rapidlyaway without any explosive effect; but if the igni-tion take place in a closed chamber, the gases firstproduced immediately penetrate the mass of thecotton, and the whole is instantaneously decomposed.Now, the object of the artillerist is to produce aforce that shall first start the ball, and then graduallyincrease its speed, until it is discharged with therequired velocity. But the explosion of gun-cottonin a gun under ordinary circumstances is so rapidthat the weapon feels the full strain before the ballmoves, and thus the chance of bursting is muchincreased.
Many suggestions have been made to overcomethis difficulty. Baron von Lenk thought he haddone so, and declared that it was only necessary togive the gun-cotton room enough in order to obtaina slower explosion. For small arms he used threador spun yarn gun-cotton, woven into a web, andenclosed the web in stiff cylinders of pasteboard.For larger guns the yam was wound round a bobbin,
a hollow tube of paper or wood. The object of this isto insure in all cases the length of chamber necessaryin the gun for the most effective explosion. In somecases different layers of the explosive were separatedby layers of paper. Baron von Lenk was able toclaim certain advantages for his gun-cotton preparedin this way. There was no residue, no smoke, andthe gun was not heated so much. It was shownexperimentally that 100 rounds were fired with asix-pounder in thirty-four minutes, the gun beingraised in temperature by gun-cotton to only 122°Fahr., whilst 100 rounds of gun-powder took onehundred minutes, and raised the temperature tosuch a degree that water was instantly evaporatedfrom the surface of the gun. 180 rounds were firedwith gun-cotton before it was thought dangerous toproceed with the experiment. But experience hasnot fulfilled the expectation of Von Lenk, and sincethe vast improvement in the manufacture caused bythe introduction of pulping, the efforts to producean explosive which can be used in guns have takenother directions. These, and the present relationof gun-cotton to fire-arms, are summarized in thearticle on Explosives .
For other military and mining purposes, however,gun-cotton is very efficacious. Until 1872 it wasthought necessary to confine gun-cotton in somestrong vessel before its full power could be de-veloped; but in that year Mr. E. O. Brown, ofWoolwich, showed that it was possible to producethe most violent explosions with gun-cotton whilein an unconfined and even wet condition. Thisdiscovery consists in starting an initial detonation,and the method now adopted is the following:—The wet gun-cotton is placed in the positionrequired, and a small cylindrical charge of drycompressed gun-cotton is laid in contact with it.This charge, called a “primer,” is provided with ahole drilled on the axis of the cylinder, into whicha detonator is fixed. A detonator is simply a per-cussion cap, such as is used with fire-arms, made alittle more powerful. It is one quarter of an inchin diameter by one and an eighth inch in totallength, and it contains five times the weight offulminating powder common to ordinary percussioncaps. Rather less than one-half of the total lengthof the copper tube is occupied by the fulminate, theremainder being reserved for a fuse. The fuse,generally prepared from specially made gunpowder,having been ignited, brings about the detonationof the fulminate; and the violent decomposition ofthe latter suffices, by the help of the primer, toexplode the mass of wet gun-cotton. In this wayexplosions of very great violence are produced.
The value of the above discovery lies in this—that the wet gun-cotton is an absolutely uninflam-mable substance, and will not burn at all till it hasbeen exposed to a high temperature for a consider-able time. Hence, there is little or no fear ofaccident under any ordinary circumstances, and yetit is quite easy to bring about explosion by thesimple means described.
Referring to the uniuflammability of this wet gun-